Recently, vehicles equipped with an electronically controlled throttle for example have a tendency to employ an accelerator position sensor which is drivingly connected to the accelerator pedal and detects the position of the accelerator pedal.
A conventional accelerator position sensor will be described here. The accelerator position sensor includes: a fixed member having a boss and fixed on the side of a vehicle body; a rotary member which has a shaft rotatably fitted in the boss and is connected to the accelerator pedal of the vehicle through a cable to rotate in response to pressing and returning operations of the accelerator pedal; a torsion spring, interposed in a position fitted on the boss of the fixed member between the fixed and rotary members, for urging the rotary member into rotation relative to the fixed member in a direction of the returning operation of the accelerator pedal by torque of the torsion spring; and a sensor unit for detecting the angle of rotation of the rotary member relative to the fixed member.
When the accelerator position sensor is placed in an engine room, as schematically shown in FIG. 4, the accelerator position sensor a is drivingly connected to a lever d of the accelerating pedal c through the cable b thereby urging the accelerator pedal c into return movement to its original position by torque of the torsion spring. Further, in the engine room, a return spring e is placed for pulling the cable b in a direction of returning the accelerator pedal c to its original position.
Meanwhile, the preferable pressing force characteristic of the accelerator pedal c is generally regarded to as having such hysteresis that the pressing force of the accelerator pedal becomes larger during the pressing operation while it becomes slightly smaller during the returning operation. As for this point, in the conventional accelerator position sensor a mentioned above, though torque of the torsion spring increases or decreases with the angle of rotation of the rotary member, hysteresis of the torsion spring in the rotational direction of the rotary member is comparatively small. However, since the operation of the accelerator pedal c creates sliding resistance in the cable b, the sliding resistance provides the pressing force characteristic having the hysteresis as mentioned above.
Specifically, during the pressing operation of the accelerator pedal c, sliding resistance in the cable b is added to the torque of the torsion spring in the accelerator position sensor a and the tension of the return spring e, thereby increasing the pressing force against the accelerator pedal c. On the other hand, during the returning operation of the accelerator pedal c, the torque and the tension are diminished by the sliding resistance in the cable b, thereby decreasing the pressing force against the accelerator pedal c.
However, when the conventional accelerator position sensor a is drivingly connected directly to the accelerator pedal c without interposing the cable b therebetween, the sensor a cannot use the sliding resistance in the cable b, and therefore is difficult to obtain the above-mentioned hysteresis.
The present invention has been made in view of the above problem, and therefore has its object of obtaining sufficient hysteresis between the pressing and returning operations in terms of the pressing force characteristic of the accelerator pedal by simply making a small change in the internal structure of the accelerator position sensor when the accelerator position sensor is drivingly connected directly to the accelerator pedal without interposing any cable therebetween.